Fuel injection valve

ABSTRACT

A fuel injector, e.g., an injector for fuel injection devices in internal combustion engines, has a valve needle with a valve-closure member which cooperates with a valve seat surface in a valve seat body to form a sealing seat, in which the valve seat body has a plurality of injection orifices that are isolated from the fuel supply by sealing seat. The valve-closure member has a pressure element in a recess facing the valve seat body, which is pre-tensioned against the valve seat body by a spring which is supported on the valve-closure member and presses a disc spring against the valve seat body, in such manner that the disc spring covers at least one of the injection orifices, and the spring element uncovers this injection orifice when the tension exerted by the pressure element is removed.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

German Published Patent Application No. 32 28 079 A1 describes a fuelinjector having two valve needles with which it is capable ofcontrolling multiple injection orifices individually. Each valve needleis pre-tensioned against a respective sealing seat by a spring. If oneneedle is raised out of its sealing seat by a certain clearance, itstrikes against a stop of the other valve needle and takes the secondvalve needle with it as the travel progresses. The two sealing seats ofthe two valve needles close different injection orifices, which may bedirected at differing angles. However, the construction is made up ofmultiple parts and two sealing seats must be manufactured to precisespecifications, which gives rise to high costs.

German Published Patent Application No. 30 48 304 A1 describes a fuelinjector for internal combustion engines having a valve needle and asecondary needle in a borehole in the valve needle. The portion of thevalve needle which, near the combustion chamber is configured as avalve-closure member, cooperates with a valve seat surface to form asealing seat that isolates injection orifices from the fuel inlet. Thesecondary needle which is guided in the valve needle also has avalve-closure member, which cooperates with a second valve seat surfaceof the fuel injector. The secondary needle is drawn towards the valveneedle by a spring that is located in the valve needle, and it alsoforms a sealing seat against the valve needle with a valve seat surfacein the valve needle. When the hydraulically actuated fuel injectorbegins to open as a result of rising pressure in the fuel supply line,the secondary needle is forced out of its sealing seat in the valveneedle and towards the sealing seat in the valve body and closes a groupof injection orifices, while another group of injection orifices isopened. If the pressure continues to rise, the valve needle is raisedout of its sealing seat and after a certain travel takes the secondaryneedle with it, the secondary needle striking against a stop of thevalve needle. All injection orifices are then opened. The disadvantageof this arrangement is that in all three sealing seats must be producedto exact specifications.

German Published Patent Application No. 31 20 044 C2 also describes afuel injector having two valve needles, which may be used to openinjection orifices in two groups. In this arrangement, one valve needleis disposed inside the other, which is constructed as a hollow valveneedle. The valve needle which is designed as a hollow needle hasinjection orifices in its end near the combustion chamber. Thedisadvantage of this arrangement is that the production of the hollowneedle is highly labor-intensive since it also has injection orifices,so that two functions, are combined in a single component, eachrequiring that the component be produced to a high degree of precision.

SUMMARY

The fuel injector according to the present invention may have theadvantage that it provides a solution for sequentially opening groups ofinjection orifices in a manner that may be inexpensive and easilymanufacturable, since the additional group of injection orifices may notrequire an additional sealing seat manufactured with a high degree ofprecision in order to be able to open separately. For Example, the angleover which the fuel is distributed in the fuel injector's jet patternmay be adjustable as a function of the valve lift.

A first circle of injection orifices may be covered by tongues in thedisc spring. Further injection orifices may have different injectionangles and may be offset with respect to one another by acircumferential angle. In such a case, initially when the injectedvolume and the load on the internal combustion engine are low, only acertain number of injection orifices having a narrow injection angle maybe opened, so that a fuel injection jet may be formed that is made up offuel jets from those injection orifices having an overall narrowinjection angle. As the load on the combustion engine increases and thedemand on the stratified charge operation of a combustion engine runningaccording to the lean-burn concept rises correspondingly, the injectionorifices of the additional orifice circle may also be opened. These maybe arranged over a larger injection angle. The fuel injection jet thatis injected overall may be delivered over a larger angle.

An example embodiment of the fuel injector according to the presentinvention is illustrated in simplified form in the drawings and isexplained in greater detail in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a section through an example embodiment of a fuelinjector according to the present invention, in the unactuated state.

FIG. 2 illustrates a section through the example embodiment of a fuelinjector according to the present invention as illustrated in FIG. 1, inthe actuated state.

FIG. 3 illustrates a top view of section along line III—III in FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates a section through a portion of an injector accordingto the present invention which faces the combustion chamber of aninternal combustion engine.

A valve body 1 may be connected by welded seam 3 to injection orificeplate 2 having injection orifices 4, and together they may form valveseat body 22. The extremity of valve needle 5 facing the combustionchamber may be furnished with valve-closure member 6. This valve-closuremember 6 may be connected to valve needle 5 via welded seam 7.Valve-closure member 6 may cooperate with valve seat surface 8 having,for example, a truncated conical shape, may be provided in valve body 1to form sealing seat 9. A pressure element 11 may be located in aninterior recess 10 in valve needle 5, and may be pressed against valveneedle 5 via a spring 12. Pressure element 11, which in this exampleembodiment may have the form of a stepped cylinder, presses on a springelement, here disc spring 13, which may have a plurality of tongues 14extending radially towards the middle. Pressure element 11 presses onthe inner extremity of these tongues 14. In this manner, disc spring 13may be pressed onto valve seat body 22, in the illustrated exampleembodiment towards injection orifice plate 2.

FIG. 1 illustrates the fuel injector in the closed state. Disc spring 13is pressed flat by pressure element 11, deformed from its shape in theunloaded condition, and tongues 14 cover outer injection orifices 15that may be arranged beneath tongues 14.

Pressure element 11 may have a collar 16 that may be used as a stop.Valve-closure member 6, which may be connected to valve needle 5 bywelded seam 7, may form shoulder 17 in recess 10 that may be used as theopposing stop. When valve needle 5 has completed partial stroke h₁,collar 16 and shoulder 17 may be in contact with one another.

FIG. 2 illustrates the same example embodiment of the present invention.The drawing represents the same cutaway section, so the same referencenumbers are used to indicate the same components. In this figure, thefuel injector is in the fully open condition.

In the fully open condition, collar 16 is in contact with shoulder 17and pressure element 11 is moved by valve needle 5. Disc spring 13 restson valve seat body 22, in this example embodiment on injection orificeplate 2. Unlike its position with the fuel injector in the closed state,as illustrated in FIG. 1, pressure element 11 is lifted from injectionorifice plate 2 over collar 16 and shoulder 17 that rests on collar 16by valve needle 5, and no longer exerts any pressure on tongues 14 ofdisc spring 13. Disc spring 13 there assumes its pre-tensioned shape andopens up injection orifices 15 that may be arranged beneath tongues 14and may have been hitherto covered by tongues 14.

FIG. 3 illustrates a section along line III—III in FIG. 1. Injectionorifices 4 and a central injection orifice 18, as well as the injectionorifices 15 that may be covered by tongues 14 of disc spring 13, may besituated in injection orifice plate 2; in the top view, injectionorifices 15 may be concealed by tongues 14 and may be thereforeindicated by broken lines. These covered injection orifices 15 may besituated in a first outer orifice circle 19 whose average circumferencemay be indicated with a broken line. Injection orifices 4 which are notcovered may be arranged in a second, inner orifice circle 20, whoseaverage circumference may also be indicated with a broken line. Discspring 13 is illustrated in the compressed state, corresponding to afully closed fuel injector. In this state, all tongues 14 are in contactwith injection orifice plate 2.

When the fuel injector is in the closed state, all injection orifices 4,15 are sealed by sealing seat 9. When valve needle 5 is raised out ofsealing seat 9 by an electromagnetic, piezoelectric, or magnetostrictiveactuator, the fuel supply to injection orifices 4 and central injectionorifice 18 is enabled, but injection orifices 15 are covered by tongues14 of disc spring 13 and remain closed. Pressure element 11 pressestongues 14 against injection orifice plate 2 and closes coveredinjection orifices 15.

After partial lift h₁, (FIG. 1) of valve needle 5, collar 16 of pressureelement 11 strikes against shoulder 17 in valve needle 5. As valveneedle 5 continues the lift, pressure element 11 may be lifted away frominjection orifice plate 2. Tongues 14 deflect away from injectionorifice plate 2 due to the natural tension of disc spring 13, and openinjection orifices 15, which have hitherto been covered. The distance bywhich tongues 14 deflect upwards may be determined by the further lengthof the lift. However, this also influences the flow cross-section tocovered injection orifices 15. If valve needle 5 is only raised by astroke smaller than h₁, only injection orifices 4, which are notcovered, may be opened if the spring force of spring 12 is designed tobe greater than the spring force of disc spring 13.

If the angle at which covered injection orifices 15 and uncoveredinjection orifices 4, 18 are disposed is varied, the overall angle of afuel injection cone may be modified. The example embodiment according tothe present invention of a fuel injector may enable high switchingfrequency; the low masses set in motion may allow rapid response. Thedesign according to the invention may be inexpensive to implement.

In a further example embodiment, disc spring 13 may be shaped withsuitable surfaces such that it may cover not only the injection orificesof first circle 19, but also the injection orifices of second circle 20,and injection orifices 4, 15 of the different circles 19, 20 may beuncovered consecutively when tension is removed, in that as tension isprogressively removed, parts of disc spring 13 may deflect upwards anduncover circle 20 before the reduced tension allows different parts ofdisc spring 13 to deflect upwards and uncover the other circle 19.

What is claimed is:
 1. A fuel injector for a fuel injection system in aninternal combustion engine, comprising: a valve seat body having a valveseat surface; and a valve needle having a valve-closure member whichcooperates with the valve seat surface to form a sealing seat; whereinthe valve seat body has a plurality of injection orifices isolated fromthe fuel supply by the sealing seat being disposed downstream from thesealing seat, and wherein the valve-closure member has a pressureelement in a recess facing the valve seat body, which pressure elementapplies pre-tension to a spring element so that at least one of theinjection orifices is covered by the spring element, and the springelement uncovers the at least one of the injection orifices when thetension exerted by the pressure element is removed.
 2. The fuel injectoraccording to claim 1, wherein the pressure element has a stop, withwhich an opposing stop of the valve-closure member comes into contactafter a partial lift of the valve-closure member, and which raises thepressure element away from the valve seat body with an additional lift.3. The fuel injector according to claim 2, wherein the stop of thepressure element is a projecting collar and the opposing stop of thevalve closing body is a shoulder in the recess of the valve closingbody.
 4. The fuel injector according to claim 3, wherein the springelement is a disc spring, and the disc spring has tongues orientedradially inward, and at least one tongue covers an injection orificewhen the radially inner ends of the tongues are pressed against thevalve seat body by the pressure element.
 5. The fuel injector accordingto claim 4, wherein at least one of the injection orifices is arrangedin a first circle covered by tongues of the disc spring.
 6. The fuelinjector according to claim 5, wherein at least one of the injectionorifices is arranged in a second circle, disposed radially inward fromthe first circle, and the at least one injection orifice of the secondcircle is covered by appropriately shaped section on the disc spring. 7.The fuel injector according to claim 6, wherein the disc spring isshaped so that it uncovers injection orifices of the different circlesconsecutively when tension is removed.
 8. The fuel injector according toclaim 7, wherein the injection orifices have differing injection angles.9. The fuel injector according to claim 8, wherein the injectionorifices have at least one of differing aperture diameters and differingaxial lengths.
 10. The fuel injector according to claim 9, wherein thevalve needle is actuatable using one of an electromagnetic actuator anda piezoelectric actuator.
 11. The fuel injector according to claim 10,wherein the injection orifices are provided in an injection orificeplate which is attached to a valve body having a sealing seat.